Putting the engine back together, pressure test failed, new new hot water valve?

[DrWin]

So anyway... It's been a while since I posted, but life got busy.
We're expecting a baby boy this June, our first kid, so the DeLorean was placed on the back burner for a while, while the house got sorted.

But the car needs to be drivable this year, so I started putting the engine back together. So far nothing I haven't been able to figure myself. But now I pressure tested the coolant system at 10psi above atm. pres. and found two leaks:

1. A pinhole size hole in the rear housing for the brand new water pump.
2. The hot water valve.

I think the rear housing for the water pump is fairly straight forward. It's an error in the casting process thats gone unnoticed. Needs replacement.
But the hot water valve puzzles me b/c it's a very, very small leak. I can barely hear it, and the system holds pressure fine for 5-10mins, but it's there. I can hear it, and when I splash water on the hot water valve I can see it, small bubbles slowly forming where the screwdriver sits in the picture below.
How much fuzz should I make about that? Are the hot water valves always leaking a little? Am I pressure testing at too high pressure? Or is this just as straight forward as the rear housing for the water pump, that it's an unacceptable error that means the piece needs replacing? If so - with which hot water valve, from which vendor - there are more than one option, I can see. (Recomandations wanted)
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[David T]

You are not supposed to pressure test with only air. You fill the system with coolant and then pressurize the system with air to 15 psi. If the leak is that small it could leak air but it should not leak coolant. As for the casting defect in the plate, replace it.

[82DMC12]

Yeah I recently went through this and found pressure testing with air only was a waste of time and made false confidence. You only find a leak if you can hear the leak and most of them are too small to make any noise. But if you fill the system up with coolant and then pressurize it, you'll find green coolant dripping wherever the leak is. Only thing that sucks is if the leak can only be fixed by opening the system again where the coolant is dripping out... then you have to drain to that level before you can fix it.

[DrWin]

So - I redid the pressuretest with coolant and the hot water valve leaked coolant like mad. I got a pair of vise grips on the valve and was able to put enough pressure on the crimps on the backside of the valve to close off the leak. So far so good, except the hot water valve is now stuck in closed position, which means I succesfuly repaired it by destroying it - sort of. Task succesfully failed!
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Still no hot water valve and no great idea with what I should replace it with. For the time being I put in a spare T-piece with a shut off valve as a place holder, while I rebuild the rest of the engine. Obv. I need to go back in...
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I thought buying the most expensive version of the valve was a move in the direction of build quality and durability. Apparently not. I wouldn't mind getting a few pointers here. Has anyone replaced the hot water valve recently and can recommend a vendor/item and/or crossover part? I'm thinking quality and durability prefered over cost. Anyone? (PM me if you'd rather.)

[Rich]

First, the all-metal valve should not leak. Yours looks fairly new. Ask your vendor for a warranty replacement. Also ask the vendor for their recommendation. They want to sell you the best parts.

Second, two non-statistically meaningful data points:

I've been running the OE-style valve (metal+plastic body with metal vacuum chamber) for over 10yrs with no leaks. It has 1 metal nipple and 1 plastic nipple.
The worst HW valve failure I've seen: A fellow D owner suffered a massive break in his OE-style valve 3yrs ago - the plastic nipple cracked off at its base while idling in slow traffic. I don't know which valve the owner replaced it with.

The all-metal design should at least prevent that particular kind of valve failure. I've been thinking that will be a good upgrade next time I flush the cooling system.

After I saw the plastic nipple failure I made sure my metal-plastic valve is arranged for minimal bending or twisting force from the coolant hoses.

[cdrusn]

I just replaced my heater valve after the outlet neck broke off. Easy job if you have the engine cover off. I got the new one from DMC Texas but noticed they
got it from somewhere sourced it from somewhere else. With the constant heating and cooling a plastic neck will become brittle. The one from DMC is all metal and fit like new.

[mark w]

I do my pressure testing with straight water. if all is ok, I drain it and then fill with coolant and test again.

[DrWin]

Thanks for all the replys. I'm gonna reach out to the vendor and have a talk about my options.

[DrWin]

Just to round this thread up - I got a new hot water valve, all metal, no leaks this time, did the pressure test with both air and then with coolant with no leaks, so this seems to have solved everything.